Isolation and Characterization of Human Conjunctival Mesenchymal Stromal Cells and Their Extracellular Vesicles

PURPOSE. The purpose of this study was to isolate and culture human conjunctival mesenchymal stromal cells (Conj-MSCs) from cadaveric donor tissue, and to obtain and characterize their extracellular vesicles (EVs) and their effect on conjunctival epithelium. METHODS. Stromal cells isolated from cadaveric donor conjunctival tissues were cultured and analyzed to determine whether they could be defined as MSCs. Expression of MSC markers was analyzed by flow cytometry. Cells were cultured in adipogenic, osteogenic, and chondrocyte differentiation media, and stained with Oil Red, Von Kossa, and Toluidine Blue, respectively, to determine multipotent capacity. EVs were isolated from cultured Conj-MSCs by differential ultracentrifugation. EV morphology was evaluated by atomic force microscopy, size distribution analyzed by dynamic light scattering, and EVs were individually characterized by nanoflow cytometry. The effect of EVs on oxidative stress and viability was analyzed in in vitro models using the conjunctival epithelial cell line IM-HConEpiC. RESULTS. Cultured stromal cells fulfilled the criteria of MSCs: adherence to plastic; expression of CD90 (99.95 +/- 0.03% positive cells), CD105 (99.04 +/- 1.43%), CD73 (99.99 +/- 0.19%), CD44 (99.93 +/- 0.05%), and absence of CD34, CD11b, CD19, CD45 and HLA-DR (0.82 +/- 0.91%); and in vitro differentiation into different lineages. Main Conj-MSC EV subpopulations were round, small EVs that expressed CD9, CD63, CD81, and CD147. Conj-MSC EVs significantly decreased the production of reactive oxygen species in IM-HConEpiCs exposed to H2O2 in similar levels than adipose tissue-MSC-derived EVs and ascorbic acid, used as controls. CONCLUSIONS. It is possible to isolate human Conj-MSCs from cadaveric tissue, and to use these cells as a source of small EVs with antioxidant activity on conjunctival epithelial cells.